An immunological approach to distinguish arthropod vivaphagy from necrophagy

Authors: ZILNIK, GABRIEL - Arizona State University; Hagler, James

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2013
Publication Date: 11/25/2013
Publication URL: http://handle.nal.usda.gov/10113/58118
Citation: Zilnik, G., Hagler, J.R. 2013. An immunological approach to distinguish arthropod viviphagy from necrophagy. Biocontrol. 58:807-814.

Interpretive Summary: IInsect predators can be valuable biological control agents for controlling key agronomic pests. However, predators that might frequently engage in carrion feeding activity will not be an asset to a viable biological control program. Scavenging activity of insect predators inhabiting economically important crops has not been thorough investigated. Understanding the prevalence of scavenging by insect predators is paramount to determining their effectiveness as biological control agents. A predator gut content assay is described that can differentiate between predator feeding on carrion (dead) and live prey. Carrion and live whiteflies and green lacewings served as targeted prey items. The carrion prey were marked with rabbit IgG protein and the live prey were marked with chicken IgG, respectively. The marked prey items then were fed to lady beetle and soft-winged flower beetle(SWFB) predators. The frequency of detection of the protein-marked prey items in the gut of the predaceous beetles was assessed for up to 48 h after feeding using a rabbit-IgG or chicken IgG-specific assay. Each IgG-specific assay detected the presence of the marker proteins in the gut of 90% of the predators up to 12 h after prey consumption. A laboratory feeding choice study was also conducted to determine if the predators prefer live or carrion prey. The study revealed that the SWFB prefers carrion prey. Finally, the laboratory observations of carrion feeding were confirmed in a field study where SWFB was observed, directly and indirectly, feeding on lady beetle carcasses. The methodologies described here are useful for future studies on various aspects of insect predation.

Technical Abstract: Scavenging activity of predators inhabiting agroecosystems has not been thorough investigated. Understanding the prevalence of necrophagy in predators is paramount to determining the effectiveness of biological control agents. A molecular predator gut content assay is described that can differentiate necrophagy from vivaphagy. Cadaver sweetpotato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) and green lacewing, Chrysoperla rufilabris Burmeister (Neuroptera: Chrysopidae) serving as targeted prey items were marked with rabbit immunoglobulin G (IgG) protein and live prey items were marked with chicken IgG, respectively. The marked prey items were fed to convergent lady beetles, Hippodamia convergens Guérin-Menéville (Coleoptera: Coccinellidae) and soft-winged flower beetles, Collops vittatus (Say) (Coleoptera: Melyridae). The frequency of detection of the protein-marked prey items in the gut of the predaceous beetles was assessed at 0, 3, 6, 12, 24 and 48 h after feeding using a rabbit-IgG-specific or chicken IgG-specific enzyme-linked immunosorbent assay (ELISA). Each IgG-specific ELISA detected the presence of the marker proteins in the gut of 90% of the predators up to 12 h after prey consumption. A laboratory feeding study was also conducted to determine the propensity that each predator species engages in vivaphagy and necrophagy. The laboratory feeding observations revealed that C. vittatus prefer carrion prey items. Finally, the laboratory observations of necrophagy were confirmed in a field study where C. vittatus was observed, directly and indirectly, feeding on H. convergens carcasses. The methodologies described here are useful for future studies on various aspects of insect predation.